advent-of-code-2018.hs

import Data.Maybe
import Data.List
import qualified Data.Set as S
import Data.Bifunctor

d01_read :: IO [Integer]
d01_read = fmap (read . (dropWhile (=='+'))) <$> lines <$> readFile "input"

d01_1 :: [Integer] -> Integer
d01_1 = sum

d01_2 :: [Integer] -> Integer
-- please send help
d01_2 = fromJust . head . dropWhile isNothing . fmap snd . scanl (\(m,r) n -> if S.member n m then (m, r <|> Just n) else (S.insert n m, r)) (mempty, Nothing) . scanl (+) 0 . cycle


d02_read :: IO [String]
d02_read = lines <$> readFile "input"

d02_1 :: [String] -> Integer
d02_1 = uncurry (*) . bimap (length . filter (any ((==2) . length))) (length . filter (any ((==3) . length))) . (\x->(x,x)) . fmap (group . sort)

d02_2 :: [String] -> [Char]
d02_2 ids = catMaybes $ (\[a,b] -> zipWith (\x y -> if x==y then Just x else Nothing) a b) $ [a|a<-ids,b<-ids,(==1) $ length $ filter id $ zipWith (/=) a b]